Millie Bobby Brown Vacations in Cabo with Family and 'Stranger Things' Castmate (& New BFF!) Sadie Sink

Millie Bobby Brown is soaking up the summer sunshine!

The young star of the Netflix sci-fi hit series Stranger Things spent some time with family and newly-added castmate Sadie Sink in Cabo, Mexico, throughout the past week.

In photos shared exclusively with PEOPLE, Brown, 13, and Sink, 15, frolic in the foamy and white turquoise waters as they hold hands while walking on the beach. During their trip, the new BFFs also spent time at the spa and dined at fine restaurants in the Grand Velas resort with family.

Brown shot to stardom (and inspired a bevy of Halloween costumes) with her portrayal of Eleven, a girl with a psychokinetic gift. The young actress also won the MTV Movie & TV Award for Best Actor in a Show and delivered an emotional speech during the surprise win in the May ceremony.

Sink — who is best known for her role in the NBC thriller series, American Odyssey — joined the hit show for season 2.

"They had so much fun at the resort, they literally never left during their visit!" a source told PEOPLE about the Stranger Things costars' time together in Cabo.

Brown also shared a sweet photo montage and caption on Instagram of the "beautiful people" that she had the "honor to spend" her vacation with.

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"Thanks again to @grandvelascabos staff! Here are some pictures to represent beautiful people that I got the honor to spend my vacation with! Love to all of you! -mills 🌸@zaringgroup #mexico #ad," wrote Brown.

The highly acclaimed cast and show — costarring Winona Ryder — earned a staggering 18 Emmy nominations and earned the SAG Award for Outstanding Performance by an Ensemble in a Drama Series in February.

While the second season of the Netflix thriller isn't set to air until October, co-creators Matt and Ross Duffer told Vulture in a recent interview that there will likely be "a four season thing and then out."